Radiometric dating practice

If you're seeing this message, it means we're having trouble loading external resources on our website. To log in and use all the features of Khan Academy, please enable JavaScript in your browser. Science Physics Quantum Physics Nuclei. Mass defect and binding energy. Nuclear stability and nuclear equations. Writing nuclear equations for alpha, beta, and gamma decay. Half-life and carbon dating.As a result, the relic has been remained controversial throughout the centuries. Carbon dating was not performed on the shroud untilwhen the process had been refined to the point where only a small amount of material needed to be destroyed. Samples were tested at three independent laboratories, each being given four pieces of cloth, with only one unidentified piece from the shroud, to avoid prejudice.

All three laboratories found samples of the shroud contain 92 percent of the 14 C 14 C found in living tissues, allowing the shroud to be dated see Figure Carbon has a half-life of If 1 kg of carbon sample exists at the beginning of an hour, b how much material will remain at the end of the hour and c what will be the decay activity at that time? The decay constant is equivalent to the probability that a nucleus will decay each second.

As a result, the half-life will need to be converted to seconds.

Another way of considering the decay constant is that a given carbon nuclei has a 0. The decay of carbon allows it to be used in positron emission topography PET scans; however, its As a result, one would expect the amount of sample remaining to be approximately one eighth of the original amount. The Calculate the age of the Shroud of Turin given that the amount of 14 C 14 C found in it is 92 percent of that in living tissue.

Here, we assume that the decrease in 14 C 14 C is solely due to nuclear decay. We enter that value into the previous equation to find t. Our calculation is only accurate to two digits, so that the year is rounded to That uncertainty is typical of carbon dating and is due to the small amount of 14 C in living tissues, the amount of material available, and experimental uncertainties reduced by having three independent measurements.

There are other noncarbon forms of radioactive dating. Rocks, for example, can sometimes be dated based on the decay of U U. The decay series for U U ends with P b P bso the ratio of those nuclides in a rock can be used an indication of how long it has been since the rock solidified.

Knowledge of the U U half-life has shown, for example, that the oldest rocks on Earth solidified about 3. Learn about different types of radiometric dating, such as carbon dating. Understand how decay and half-life work to enable radiometric dating to work. Play a game that tests your ability to match the percentage of the dating element that remains to the age of the object. Skip to main content.

# Half life and radiometric dating practice problems

Sections Learning Objectives. Half-Life and the Rate of Radioactive Decay. Activity, the Rate of Decay. Carbon is naturally in all living organisms and is replenished in the tissues by eating other organisms or by breathing air that contains carbon.

At any particular time all living organisms have approximately the same ratio of carbon 12 to carbon 14 in their tissues.

Radiometric dating practiceWhen an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death. Radiocarbon dating can be used on samples of bone, cloth, wood and plant fibers.

The half-life of a radioactive isotope describes the amount of time that it takes half of the isotope in a sample to decay. Finally, students complete a project that examines the science fiction genre in relation to real-world science concepts and topics. This lesson plan makes the connections between the worlds in science fiction and students' real world explicit by asking them to explore the underlying science that supports the fictional world and considering its relationship to the real science in today's society.

It presents a teaching idea for using a digital organizer to walk students through the mapping and writing of an argumentative essay.

Users can also determine the age of different objects such as fossils and rocks by percentage of parent nuclei remaining. The text describes how scientists are attempting to use several pieces of evidence to pinpoint when a mass extinction event occurred at the end of the Permian Period.

The text points to a connection between increasing volcanic eruptions, an increase of carbon dioxide in the atmosphere, and their relationship to mass extinctions before alluding to the signs of how human activity could be pushing Earth towards one.

Grade Level s : 7. Intended Audience: Educators.

The stable form of carbon is carbon 12 and the radioactive isotope carbon 14 decays over time the amount of time that it takes half of the isotope in a sample to decay. In the case of radiocarbon dating, the half-life of carbon 14 is 5, years. Half-Life and Practice Problems. 1. Half-Life and Radiometric Dating; 2. Rate of Decay The time required for half the nuclei in a sample of a. The half-lives of many radioactive isotopes have been determined Remember, the half-life is the time it takes for half of your sample, no matter Understand how decay and half life work to enable radiometric dating. There are two types of half-life problems we will perform.

Instructional Time: 3 Hour s. Resource supports reading in content area: Yes. Keywords: half-life, radioactive, radiometric, radioactive, dating, decay, carbon, isotope, element, rock, cycle, geologic, time, era, eon, superposition, MEA Model-Eliciting Activityproblem solving.

Please log in using the Sign in section on top then try again. This resource requires special permission and only certain users have access to it at this time. Feedback to Students Feedback to students is provided throughout the lesson. Summative Assessment Use the attached rubric. Learning Objectives Students will: Produce a clear and coherent written response appropriate for a professional scientific audience. Investigate the process of radioactive dating and describe how this method can be used to determine the age of the Earth and many other objects.

Solve multi-step real-life mathematical problems using decimals and proper operations to estimate and then properly calculate the age of various materials. Prior Knowledge Students should: Be familiar with the rock cycle and the three types of rocks igneous, metamorphic, and sedimentary.

the following: Explain radioactive half-life and its role in radiometric dating; Calculate radioactive half-life and solve problems associated with radiometric dating next, and so on. Nuclear decay is an example of a purely statistical process. Keywords: half-life, radioactive, radiometric, radioactive, dating, decay, carbon, time, era, eon, superposition, MEA (Model-Eliciting Activity), problem solving.

Understand the relative ages of layers from the law of superposition and what fossils are, but need not yet know exactly how the absolute ages of rock layers or fossils are determined. Have knowledge of the geologic time scale and the names of the eons throughout history. Instructional Suggestions This lesson is intended to be completed in 1.

The lesson plan indicated below is presented in time-oriented breakdown: min. Begin class with a brief introduction to the concept of radioactivity.

If you do not have access to these, a class discussion, read aloud from an appropriate selection of textor other video review would be appropriate. Be sure to define the following words with the class: radioactive, isotope, radioactive decay.

Discuss the possible uses of radioactive material in science. BBC Bitesize goes on to explain radioactive dating in the following sectionthough it is only text and images, without an interactive video.

## Radioactive Dating: Half-Life & Geologic Time

Introduce the MEA lesson concept: Your students' help has been requested by the Natural History Foundation in order to help them select the proper elemental isotopes to use in their radioactive dating process. The students must decide which elemental isotope is best suited for determining the absolute age of one of three ancient discoveries.

Inform students that they will be completing a full essay written response with their decisions and reasoning at the end of this project. Arrange students in groups of to prepare for the project it may be helpful to have predetermined groups ready. Allow students in each group to read the client letter.

This image will help the students in their understanding of the client letter as well as developing their response essay. Ask the students what they think of the information, and how would they determine which elemental isotope is the best for each item? Use their responses to transition into the next section. Define and explain "radioactive dating" and "half-life.

Key Concept: A half-life is a set amount of time after which half of the radioactive element will have disappeared because it turned into a new element! Key Concept: Radioactive dating is when scientists use the amount of radioactive materials in a rock or fossil and the half-life duration to calculate the absolute age of the rocks or fossils.

Teacher Demo: 8 red blocks, with a year half-life have 8 blue blocks ready to represent the daughter element After years, how many red blocks? Answer : years. They can then complete calculations to see how many half-lives have passed, which will tell them the age of the rock!

Calculating Absolute Age.

With your class, complete the following examples on the board: Simple Example: If a rock sample has g of radioactive material with a half-life of years, how much of the radioactive material will remain after years? What about after years? Real-Life Example: A scientist finds a gram rock composed of grams of Lead and 50 grams of Uranium They know that the rock used to be entirely made of Uranium The half-life of U is million years.

How old is the rock? Start with g. After 1 half-life, how much Uranium will I have left? What about after a second half life? Take how much Uranium we have left g and divide that by 2.

Is that how much the scientist found in the rock? Yes And how many half-lives had to pass to get us to 50g? Answers : Yes; 2 half-lives. So, if each half-life is million years, and we did 2 of them, how old is our rock? If available, use manipulatives whenever they will be of assistance. Use the readiness questions to be sure each group understands the assignment.

They must think of a rationale to explain why they would select a particular elemental isotope for each of the three items being dated. You may discuss the readiness questions with the entire class, or go over them with each group separately. A teacher of advanced classes may be able to point the group to the questions and allow them to discuss only amongst each other, without direct instruction from the teacher.

Once the students understand what is requested of them, allow them to work in their groups. They should have a written explanation of the steps used to make this selection. The response letter must be written in paragraph form as a professional response to the client. Students must have 1 written paragraph for each of the items to be dated. This paragraph must provide the rationale as to why the particular element was selected.

Collect all student work and wrap up: Ask students which choice they made and why they chose it. Open discussion with the entire class. What item do they think would be the oldest?

Which one would be hardest to date? Block Day 2 min. Begin class with a review of Radioactive Dating and Half-Life. The BrainPop "Carbon Dating" video is a great review tool. If you do not have access to this, a class discussion, read aloud from an appropriate selection of textor other video review would be appropriate. Complete the BrainPop post-lesson quiz as a class.

If you do not have access to this, a few review demonstrations using the blocks and some half-life calculations would be appropriate. Inform your students that you have heard back from the Natural History Foundation. They have more work for you! Arrange your students in the groups from the first section of this MEA. Once again, the group will have to complete a response letter indicating the elemental isotope they feel should be used on each of the new items.

The new data only has 2 items, so students must complete a 4 paragraph response essay.

Use the table below to help solve the problems. 1. If a sample contains g of a radioactive isotope, how much will be left after 3 half lives? 2. If a sample. Included in these are two which use C as the example problem to be solved. of thumb is that a radioactive dating method is good out to about 10 half-lives. Radiometric dating is a means of determining the "age" of a mineral If a half life is equal to one year, then one half of the radioactive element will have For example, uranium is an isotope of uranium, because it has 3 more.

Collect student essays and review responses as a class. The MEA has been completed. If using block scheduling, this allows you approximately 1 hour of the same class day to review concepts with the class, do reading on related topics, watch an educational video, or any other desired lesson reinforcement. Supplemental Reading The BrainPop website has numerous information associated with the videos presented in the lesson plan.

Advanced students may be able to learn from this information. Answering these questions should aid you in selecting an elemental isotope to be used in dating these objects: Ground sloth During what time eras or epochs do we think the giant ground sloth lived? About how many years ago was that?

## Half-life and carbon dating

Stone slab from Antarctica What type of rock is the stone slab from Antarctica? In what eon were most of the rocks nearby this location formed?

Petrified trees Although petrified trees used to be alive, what are they made of when we find them in the present day? In what era did most of the trees from the park in Arizona live? The Pleistocene goes from 11, Rubidium and Uranium; they are not accurate at dating objects less than 10 million years old.

Stone slab from Antarctica Igneous Archean Eon 2.

Also, C dating only works on objects up toyears old. Petrified trees Minerals Triassic Era Million Years Ago Carbon Only works on matter that was once living The minerals that replaced the tree were never living Also, C dating only works on objects up toyears old.

Reading Passage 1 See attached Client Letter 1. Attention Geologists, The Natural History Foundation NHF is a company that works to ensure the accuracy and validity of scientific research and claims. The three items that must be dated are as follows: 1. Thank you for your help! Sincerely, Mica D. What is the client asking your team to do?

What are the three objects being dated by the company? What things do you need to include in your response?

Our client wants us to select an elemental isotope to use for radioactive dating of three different objects. The three objects are the remains of a giant ground sloth, a large stone found in Antarctica, and a petrified tree. In our response, we need to complete a 5 paragraph essay that explains which elemental isotope we feel should be used to date each of the three objects.

We also have to explain why we selected the isotope for each object.

Yes... Likely... The easier, the better... All ingenious is simple.